What Is Road Base?
Road base (also called aggregate base course or ABC) is a compacted layer of crushed stone, gravel, or recycled material placed beneath pavement, asphalt, or concrete surfaces. It provides structural support, distributes loads evenly, improves drainage, and prevents the surface layer from settling or cracking.
A properly installed road base is critical for the longevity of any paved surface. Without it, driveways, roads, and parking lots are prone to premature failure, rutting, and frost heaving in cold climates.
Road Base Calculation Formulas
Road Base Material Types
| Material | Density (tons/yd³) | Best Use |
|---|---|---|
| Crushed Limestone | 1.35 | General purpose, driveways, roads |
| Recycled Concrete | 1.40 | Budget-friendly, eco-friendly option |
| Crusher Run | 1.45 | Superior compaction, parking lots |
| Gravel Base | 1.30 | Light traffic, pathways |
| Dense Grade Aggregate | 1.50 | Heavy traffic roads, highways |
Recommended Depth Guide
- Residential driveways: 4-6 inches of compacted road base.
- Parking lots: 6-8 inches for light vehicle traffic.
- Rural roads: 6-10 inches depending on soil conditions and traffic volume.
- Heavy commercial/industrial: 8-12 inches or more with sub-base layers.
- Clay or soft soils require thicker base layers (add 2-4 inches to standard recommendations).
Frequently Asked Questions
What is the compaction factor for road base?
Road base material typically compacts 10-20% when properly rolled and vibrated. This means you need to order 10-20% more loose material than the final compacted volume. A compaction factor of 15% is standard for most crushed stone bases.
How many tons of road base do I need for a driveway?
A typical 60 x 12 foot driveway with 6 inches of compacted base requires approximately 720 cubic feet (26.7 cubic yards) of loose material, which weighs about 36-40 tons depending on the material type.
Can I use road base without pavement on top?
Yes, compacted road base makes an excellent gravel driveway or parking surface on its own. Crusher run is particularly good for this because its mix of fine and coarse particles locks together tightly when compacted. Apply in 3-inch lifts and compact each layer.